1. Field of the Invention
The present invention relates to a fuel reformer, and a waste processing system including reformer, especially to a direct heat exchange type, non-catalyst fuel reformer, and a waste-to-energy incineration system in which a direct heat exchange type, non-catalyst fuel reformer is adopted.
2. Description of Related Art
As a fuel reformer for reforming source fuel such as hydrocarbon material to a gas containing hydrogen, an indirect heat exchange type fuel reformer or a direct heat exchange type reformer has been largely used. Further, there are two types of fuel reformers, that is, a fuel reformer using a catalyst and a fuel reformer which does not use a catalyst.
In an indirect heat exchange type fuel reformer, a reaction tube and a burner are provided. While the reaction tube is heated by the combustion gas from the burner, raw gas enters the reaction tune at an end of the reaction tube. Further, the raw gas is partially oxidized (so-called partial combustion), and reformed to gas including hydrogen, either by using a catalyst or by using coolant steam on a basis of hydrothermal reaction.
On the other hand, in a direction heat exchange type fuel reformer, the heat required for reforming raw fuel is directly given to raw fuel flowing in a fuel flowing path by partial oxidization, which results in a high temperature gas of raw fuel. The high temperature raw fuel (hereafter, referred to as fuel for simplicity) is reformed to gas including hydrogen, either by using a catalyst or by using steam coolant on a basis of hydrothermal reaction. In a chemical industrial plant, a direct heat exchange type reformer is mainly used.
In the method of using catalyst, since the catalyst can lower the reforming energy, that is, the reforming temperature to about 700.degree. C., only 20% of the fuel is consumed for partial oxidization.
In the method of using no catalyst, due to the absence of catalytic energy saving effect, more than 20% of the fuel is required for partial oxidization in order to obtain the reforming energy, that is, a reforming temperature as high as 1300.degree. C.
One of features of the waste-to-energy incineration system is that the generated heat changes due to changes of the amount of waste to be processed, depending on the day, the season or the year, which is particular to the waste processing. Further, since the waste processing is requested to be performed without stopping of operations, in addition to the above-mentioned feature, a maintenance-free composition or structure is strongly required for the waste-to-energy incineration system. For satisfying the above-mentioned requirement, each apparatus composing the system should be composed of long-service parts. To realize the above-mentioned apparatuses, the method in which a catalyst is not used, is advantageous. However, in this method, it is indispensable to produce energy necessary for reforming fuel gas by partially oxidizing more than 20% of fuel in order to reform fuel gas with the partial oxidation heat itself of fuel gas. (Hereafter, a fuel reformer mainly indicates a fuel reformer without a catalyst, in which more than 20% of fuel is partially oxidized.)
An existing fuel reformer has been usually used, for example, in a gas turbine power generation system. Further, a power generation system in which a fuel reformer is provided, is disclosed in JP-A-286835/1990, JP-A-332166/1993 and JP-A-332167/1993.
Since the previously-mentioned indirect heat exchange type fuel reformer includes a burner for heating a reaction tube, such a fuel reformer has a problem in that the size of the apparatus becomes large, and an external heat source has to be provided.
On the other hand, a direct heat exchange type fuel reformer is superior to an indirect heat exchange type fuel reformer in the point that the fuel itself produces a heat source for reforming fuel gas by partially oxidizing the fuel. In addition, due to the absence of a burner and a reaction tube, the size of the fuel reformer can be reduced in comparison with the indirect heat exchange type.
One of the objects of the waste-to-energy incineration system is to burn waste and decrease the volume of waste, without polluting the environment. Another object is to generate power by utilizing the heat generated in burning waste. Therefore, it is very important to remove hazardous material from exhaust gas generated in an incinerator. In particular, removal of dioxin has been a very pressing subject.
The apparatuses disclosed in JP-A-286835/1990, JP-A-332166/1993 and JP-A-332167/1993 are mainly used for a gas turbine power generation system. The above-mentioned subject is out of the question with these devices because of using fuel different from the waste. Therefore, the conventional reformers are not based on the same subject matter. Further, since various kinds of waste are burned in an incinerator, the amount of generated heat changes hour by hour, month by month and year by year. Consequently, since the amount of fuel fed to a fuel reformer changes, corresponding to the amount and the components of gas exhausted from the incinerator, an existing direct heat exchange type fuel reformer has a problem, that, a fire-proofing brick structure part inside the incinerator is easily damaged and worn out due to the changes of the generated heat.